SCR top connector

ABSTRACT

A mechanical joint assembly for a steel catenary riser (SCR) is disclosed. The lower section of the mechanical joint assembly is comprised of steel or alternate high strength components, rather than elastomers to absorb the high loads and increase life of the unit. The lower mechanical joint assembly provides for reduction of bending moments and resulting fatigue stresses at the SCR top by removing resistance to movement in all angular directions, providing increased lateral and in-plane angles to provide increased construction tolerances for the pipeline approach corridor. Pipeline approach angle increase is accommodated by providing dual orthogonal trunnions in addition to an axial swivel. The upper mechanical joint assembly, acting without riser tension loads, allows for the use of either flexible high-pressure pipe or swivel arrangements to accommodate angular flexure before the rigid deck piping. As a system, the mechanical joint assembly provides for upstream and downstream valving for safety and maintenance without decreasing the fatigue life of SCR&#39;s.

The present application is a § 371 of PCT/US00/10938 filed Apr. 20,2000, which claims the benefit of U.S. Provisional Patent ApplicationSerial No. 60/130,579 filed Apr. 21, 1999.

FIELD OF THE INVENTION

The invention relates to an SCR Top Connector Assembly for thearticulating connection of a conduit, such as an offshore flowline orpipeline used in the petroleum industry, to a foundation subjected todifferential motions of the conduit and structure. More particularly,this invention relates to a subsea pipeline with significant unsupportedlength, termed a “steel catenary riser” (SCR), which would utilize theSCR Top Connector Assembly to connect the SCR to a fixed or floatingstructure, including several parts that work together to provide fluidcommunication from the SCR to the platform piping system, to allowdynamic and relative motions of the SCR and the structure.

BACKGROUND

In the offshore oil and gas sector, recent developments in deeper waterdepths have demonstrated the need for improved solutions for theeconomic attachment of a flowline, or pipeline, to a structure, whetherfixed or floating. Initial development utilized flexible pipe from theseabed to the floating platform; however, many operators have begun tofavor the potential safety and savings offered by the use of steelcatenary riser (SCR) configurations, wherein the pipeline is suspendedfor some distance off the seabed and connected to the structure, orfloating platform.

The prior art assembly of SCR flexible joints greatly limit the approachcorridors of flowlines due to the degree of dynamic angular movementthat can be accommodated. Manufacturing and installation tolerancesoffshore in deep water leave little dynamic allowance in the prior artonce the static offset of floating vessels are included. The angularlimits of the prior art assembly pose difficulties for the design andconstruction engineers of offshore pipelines to ensure that theinstallation tolerances, fabrication tolerances, and operationalconditions will not exceed the limits of the flexible joint andpotentially lead to failure of the SCR. If the limits of the flexiblejoint are exceeded, all flexibility is lost and the SCR is exposed tovery large bending moments resulting in dramatically and unpredictablyshortened fatigue life, thereby leading to possible failure of the SCRbelow the flexible joint near the platform. Failure of an SCR inpetroleum gas service or an SCR connector component without a viablesafety shutdown valve would pose a very high risk of fire and loss oflife as the gas in the pipeline (extending frequently 60 miles from thehost platform) would be released at the base of the manned structurewhich contains sources of ignition. Although a gas leak may be morehazardous, failure of a SCR in petroleum liquid service would lead to afairly large oil spill in open water since much of the oil in thepipeline would be siphoned out of the pipeline by the low pressure wakeof the SCR falling to the seabed. Additionally, the oil would beexpelled by expanding gases within the oil, as well as normal moleculardiffusion.

It is an object of this invention to have features which greatlyincrease safety over present art by eliminating a risk of gas leakage atan offshore platform by allowing the use of normal and proven safetyvalves. This reduces the potential for fire, and eliminates potentialoil leakage into seawater when used with oil lines. Current SCR flexiblejoints utilize elastomeric and metal laminations, which provide pressurecontainment. The same elastomeric materials serving as seals must absorbthe full SCR vertical reactions while repeatedly being deflected underhigh vertical loads. The vertical loads can reach 100 tons due to thesuspended riser weight, motions of the SCR subjected to continualenvironmental loading, and relative platform movements. Under cyclicloading, the elastomeric elements containing the fluids, under variousconditions of temperature and pressure, may likely become a path for gasor oil leakage which would result in oil contamination of thesurrounding seawater or leakage of gas at the base of the offshoreplatform. This would cause a gas plume and a risk of sinking thefloating vessel or risk of fire to the structure overhead. If asemi-submersible were to sink at a corner, it would likely lose tendonsand capsize. The industry considers systems with moving elastomericparts to have maintenance or replacement requirements at some point intime and therefore leakage considerations are valid considerations withelastomers subjected to high cyclic compressive and shear loads actingas the sole safety barrier under pressure. Although platform pipingvalves can be closed on the platform side in the present art flexiblejoint, it is presently not considered possible to provide a safety blockvalve below the prior art flexible connector due to the high axial loadsand high bending moments at the top of the SCR. These loads would beextremely taxing to the integrity of the valve and would not be areliable safety feature.

A lower block valve, though not practical with present (prior art)equipment, would prevent elastomer leakage from causing the entirepipeline or SCR from back-flowing gas into the platform creating anuncontrollable hazard to life of platform personnel. In fact, thebending moments and related stresses are so high in the top section ofthe SCR, below the flexible connector, that specially fabricated tapered‘stress’ joints are required to minimize the stress concentrationfactors in these installations. The stress intensification values areprimarily due to the high bending moments resulting from the flexuralhigh stiffness of the prior art SCR Top Connector to which the SCR isconnected. The high bending moments are primarily a result of the highrotational stiffness of the laminated elastomeric elements beingdeflected laterally in shear while under high compression loads.

The replacement, or leakage failure correction, of the elastomers withinthe prior art assemblies is essentially impossible by the platform crewor by means that can be flown offshore to the site, or otherwise beeffected in a short duration to reduce a prolonged platform hazard. Itis a further object of this invention to eliminate elastomers from themultiple role duties of high load absorption, flexural cycling, andhigh-pressure containment of petroleum liquids and gases.

To correct fluid leakage of the prior art assemblies, it is necessary toremove the SCR and its associated pipeline from service by shutting inthe platform and purging the section in order to provide a safe repairenvironment. It is also necessary to employ the use of costly offshoredeepwater service equipment with sufficient lifting capacity to removeand re-attach a new assembly since the elements are not able to bereplaced by the platform crew in a timely fashion in the prior artassemblies.

Prior art is described in part by the following patents:

U.S. Pat. No. 3,692,337 Flexible Coupling, Mischel; Howard T., SanDiego, Calif. Sep. 19, 1972.

U.S. Pat. No. 3,952,526 Flexible Supportive Joint for Subsea RiserFlotation, Watkins; Bruce J., Rancho Palos Verdes, Calif. Apr. 27, 1976.

U.S. Pat. No. 5,791,695 Flexible Joint for Facilitating Bending ofTubular, Snider; David A., Hurst, Tex. Aug. 11, 1998.

U.S. Pat. No. 5,615,977 Flexible/Rigid Riser System, Moses; Charles J.,Alvarado, Tex. Apr. 1, 1997.

U.S. Pat. No. 5,628,586 Elastomeric Riser Tensioner System, Arlt, III;Edward J., Arlington, Tex. May 13, 1997.

U.S. Pat. No. 4,105,266 Laminated Bearing with Plural Modulus Layer,Finney August 1978.

U.S. Pat. No. 4,759,662 TLP Marine Riser Tensioner, Peppel July 1988

It is a further object of the present invention to minimize thepotential for fire risk and loss of life; oil spills, uncontrolled andextended leakage, high maintenance costs and pipeline/platform downtimeduration.

It is another object of the present invention to provide a system withautomatic shut-in safety block valve capability on each side of anynon-metallic elements which may be subject to leakage.

It is a further object of the present invention to increase theallowable dynamic displacement angles to reduce the chance of bottomingout and causing premature SCR fatigue failure.

It is an additional object of the present invention to minimize the highstress levels which occur at the base of the prior art flex joint toeliminate the needs for specially fabricated tapered stress joints andprovide extended fatigue service life of the SCR by reducing the topsection fatigue moments.

It is yet another object of this invention to isolate the high loads dueto the suspended risers from acting on flexible or elastomeric elements.

It is also an object of this invention to use load isolated swivelswhich convert pendular motions to rotary motion and allow system usewhen pressure and diameter restrictions prevent the safe use of flexiblepipe.

It is also an object of the present invention to provide external meansof dynamic high-frequency damping.

It is also an additional object of the present invention to allowessentially unlimited pipeline approach angle to the pre-installedattachment of steel catenary risers on platforms.

SUMMARY OF THE INVENTION

The present invention includes a mechanical joint assembly in which theload-absorbing base is composed of steel or alternate high strengthcomponents, providing a higher level of safety and spill prevention thanis offered by prior art. The present invention further provides for theuse of valving upstream and downstream of the only non-metallicmaintenance item(s) without decreasing fatigue life. The presentinvention also reduces bending moments and resulting fatigue stresses atthe SCR top by removing resistance to movement in all angulardirections, with increased lateral angles to provide increasedconstruction tolerances for the pipeline approach corridor. The presentinvention allows the use of increased angles of in-plane dynamic motionwith elimination of large vertical SCR supported weight reactions fromacting on elastomeric components.

The safety requirement, of preventing uncontrolled back feeding of thepipeline or SCR and thus averting fire and loss of life, is achieved byabsorbing all reactions of the SCR prior to subjecting elastomers topressure containment requirements. By isolating the high loads,downstream and upstream, remote or manual-operated, shut-off valves canbe provided to fully isolate any leak within a short section withoutsacrifice of the system fatigue life. Preventing any block valve fromabsorbing the high SCR environmental reactions minimizes the chance ofvalve leakage or malfunction.

The long service outage and high maintenance costs are eliminated byproviding the above noted block valves, limiting possible maintenanceitems to simple diver replacement components without the need for anyoffshore service vessels.

The present invention therefore separates the design requirements ofhigh load control and that of allowable motion and flexure. Theseparation point may involve several means, which are described hereinalong with more specific details of the preferred embodiments.

In the preferred embodiment, increasing the allowance for the pipelineapproach angles is accommodated in the lower base by providing dualorthogonal trunnions in addition to an axial swivel to compensate forinstallation rotational misalignment. A comparison can be made betweenthe present invention and that of the prior art: when the normalconstruction tolerances are subtracted from the systems three to fourtimes greater allowable dynamic angles are achieved by the proposedsystem than when compared to the prior art. This increase greatlyreduces the chance of exceeding the flexure rates associates with highstress levels when pressure limits are exceeded.

Doubling the load carrying capacity is achieved in the present inventionby providing a robust design with heavy cross sections and gradualsection transitions in the base to minimize stress levels and, stressintensification factors, thereby providing improved fatigue resistanceand load handling.

Elimination of specially prepared tapered stress joints is achieved bythe omission of elements which resist the angular motion of the SCR byhigh-bending moments, as is in the case of the prior art assembly, andthe substitution of either low friction, higher-paired pivot systems,bearings, bushings, low-friction coatings, or ultra smooth surfaces.Systems above the base are provided to absorb the angular rotationwithout tensile loading and with low rotational stiffness.

The Top Connector Assembly may include an optional damping system tocurtail high frequency motion. The damping system is subjected to thehigh SCR reactions and may be maintained, or replaced, without shut-inof the system by a diver and small platform-mounted equipment. Becausethe fluid medium for damping may be seawater, or other benign fluids,failure of the system in any way does not constitute an emergency. Themaintenance could include only the installation of a new damper.

The benefits afforded by the objects of this invention, as defined,clearly address safety concerns of the prior art devices and increasethe operational limits and reliability by allowing greater SCR motionswith less constraint while eliminating present concerns of installationtolerances. These features in turn allow for measurably larger SCRstorm-induced dynamic movement angles with safety.

The assembly of the preferred embodiment of the present invention iscomposed of several principal parts which make up the load absorbingbase and the flexible assembly:

(A) A pressure carrying body which is attached to the uppermost portionof the SCR riser. This component incorporates a pair of male trunnions,which are structurally connected to the pressure containment body andlocated at opposite sides of the pressure-carrying body, which is anextension of the SCR pipe. The trunnions include features of higherpaired rolling motion that provide essentially frictionless motion.Alternate arrangements when friction is less significant due to lightSCR reactions include bearings, or lubricated bushings for thetrunnions. Rotary motion of the pressure containment body is provided byinterior coatings or other means to prevent locked-in torsional stressesduring installation;

(B) A trunnion adapter, which consists of a female trunnion on theinterior surface, which mates with the pressure containment body andadditionally contains a second “outer” male trunnion pair, as describedabove, located on the outer surface and on an orthogonal plane (aperpendicular plane) to the interior trunnions;

(C) A foundation receptacle that is attached to a foundation of thestructure and accepts the outer surface trunnion pair of the secondpart. The trunnions act in the principle of a universal joint and allowsmovement in any angle;

(D) Rounded-knife edge pivot, bearings, or bushings may be utilized toprovide for rotation of the trunnions to reduce the friction to thedegree required for the application;

(E) An optional damper, which can be utilized to absorb high frequencymotions and prevent resonance of an undesirable mode due to dynamicexcitation of the environment may be included in the assembly as asystem approach solution;

(F) A series of swivels converting pendular to rotational motion,flexible pipe, or other means of the prior art, is incorporated into theassembly above the load absorbing base to provide flexure. The loadrequirements for the swivels and/or flexible pipe are significantlylower because the external loads have been absorbed by the trunnionassembly and associated components;

(G) The swivel or flexible pipe assembly may be preferentially protectedat each end with automatic or manual valving at the upstream anddownstream ends for automatic and manual shut-in safety withoutcompromising the fatigue life of the system.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature and objects of the presentinvention, reference should be made to the detailed description of thepreferred embodiment which references the following drawings of whichlike parts are given like reference numerals and wherein:

FIG. 1 depicts a typical SCR application showing the major elements ofthe present invention with use of a flexible pipe as the flexibleassembly;

FIG. 1a depicts a typical SCR application showing the major elements ofthe present invention with use of a rotary swivel system as the flexibleassembly;

FIG. 2 depicts a cut away view of the SCR Top Connector Load AbsorbingBase of the preferred embodiment of the present invention, denoting theprinciple components and indicating the magnitude of allowable motions;

FIG. 3A depicts the SCR pressure carrying extension with the innertrunnions of the preferred embodiment of the present invention;

FIG. 3B is an end view of the carrying extension shown in FIG. 3A;

FIG. 3C depicts an alternate embodiment of the SCR pressure carryingextension;

FIG. 3D is an end view of the carrying extension shown in FIG. 3C;

FIG. 4A depicts the top view of the outer trunnion adapter of thepreferred embodiment of the present invention;

FIG. 4B depicts the side view of the outer trunnion adapter of thepreferred embodiment of the present invention;

FIG. 5A depicts the plan view of the foundation receptacle of thepreferred embodiment of the present invention with installation of SCRattached top connector components partly in phantom line;

FIG. 5B depicts the front view of the foundation receptacle of thepreferred embodiment of the present invention;

FIG. 5C depicts the side view of the foundation receptacle of thepreferred embodiment of the present invention;

FIG. 6 depicts alternate trunnions or bearings, a higher pairing extralow friction trunnion, a bearing and a bushing subassemblies (FIGS. 6A,6B, and 6C, respectively) for the pressure-carrying body and thetrunnion adapter of the preferred embodiment of the present inventionare determined;

FIG. 7 depicts the manner of assembly in which the reliefs of the outertrunnion adapter 630 of the preferred embodiment of the presentinvention are determined;

FIG. 8 depicts an optional damper assembly of the preferred embodimentof the present invention having three views: FIG. 8A, a top view; FIG.8B, a front view; and FIG. 8C, a side view;

FIG. 9A depicts damper details of the preferred embodiment of thepresent invention;

FIG. 9B depicts a detail of the preferred embodiment of the presentinvention;

FIG. 10 depicts the Flexible Assembly incorporating a rotary swivelsystem arrangement of the preferred embodiment of the present invention;and

FIG. 11a depicts the side exterior of a single-seal, high-pressurerotary seal option typifying the rotary swivel system.

FIG. 11b is an end view of the rotary seal shown in FIG. 11a;

FIG. 11c is a cross-sectional cutaway taken along lines A—A in FIG. 11a;

FIG. 11d is a detail of a portion of the rotary seal cross-section ofFIG. 11c.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The SCR application is depicted in FIG. 1 wherein the water surface 100supports the floating structure 300 above the seabed 200. The floatingstructure 300 is connected to the seabed pipeline by the steel catenaryriser (SCR) 400 connected to deck piping 500 by the Top ConnectorAssembly 600. The Top Connector Assembly 600 connects the SCR 400 to thedeck piping 500 via the lower valve 800 which is connected to one end ofa Flexible Assembly 700. In FIG. 1, the Flexible Assembly is composed asa flexible pipe. The other end of Flexible Assembly 700 is connected toa topsides closure valve 900. FIG. 1A depicts the Flexible Assembly tobe composed of a rotary swivel system configured to absorb thetranslation and pendular motions of the lower valve 800 as in the caseof large diameter and high-pressure risers.

The preferred embodiments of the present invention, as shown in FIG. 2,use a universal type joint SCR Top Connector Assembly 600 Load AbsorbingBase, which is attached to the floating structure 300 via the foundationsupport 610. Top Connector Assembly 600 includes a pressure containingSCR extension 620, which connects the SCR riser 400 for fluid connectionto the deck piping 500. SCR riser 400 is connected to the pressurecontaining SCR extension 620 by welding 621 or other appropriatemechanism. A trunnion adapter 630 or outer trunnion forms anintermediate structure between an inner trunnion 625 of the SCR TopConnector Assembly 600 and the foundation support 610. A bearingassembly 640 is mounted to the orthogonal trunnions of the outertrunnion assembly 630. The pressure containing SCR extension 620trunnions are depicted with a bearing assembly 641 option covered by acover plate 650.

A remote operated vehicle, or ROV, or other diver-friendly retainer 660is shown in the closed position. The retainer 660 retains the trunnionbearing assembly 640 in the foundation support 610. The retainer 660prevents the trunnion adapter or outer trunnion assembly 630, and hencethe SCR Top Connector or swivel assembly 600, from being moved out ofthe foundation support 610.

FIG. 3A details a portion of the embodiment shown in FIG. 2. Threepieces, SCR extension assembly 620, inner trunnion housing 680 andcollar 690, are shown in FIG. 3A. For assembly, inner trunnion housing680 slides over the outer surface 671 of SCR extension assembly 620 andis held in place by collar 690, also surrounding surface 671 and boltedby bolts 691 to SCR extension assembly 620.

FIG. 3B illustrates a variation of the SCR extension assembly 620. InFIG. 3A, the upper flange 670 is shown connected to a SCR extensionassembly 620 with a trunnion 681 extending from an inner trunnionhousing 680, such as by casting, thereby allowing axial rotation in oneplane. The inner trunnion housing 680 is free to rotate around the axisof SCR extension 620 because pressure containing SCR extension assembly620 is not welded or otherwise connected directly to inner trunnionassembly 680 but is merely juxtaposed to it freely permitting therotation of inner assembly 680 around the axis of SCR extension 620(FIG. 3A). The vertical movement of the SCR extension assembly 620 isrestricted by the collar 690 (FIG. 3A), which is attached to SCRextension 620 by bolting 691 or other appropriate means. Alternatively(FIG. 3B), the upper flange 670 may be connected to a sufficiently thickpressure retaining segment 620′ which incorporates the inner trunnion681 as an integral component without a separate trunnion assembly 680 orcollar 690, although rotation is thus eliminated in this case for theSCR extension relative to the inner trunnion 680, as in FIG. 3A.

FIGS. 4A and 4B show the details of the trunnion adapter or assembly630, which transmits forces to the foundation support 610 from the SCRriser extension assembly 620. Trunnion adapter 630 comprises externalsupport or outer structural envelope 631 having reliefs 632 cast orotherwise machined therein. Reliefs 632 are sized to receive trunnion681 (FIGS. 3A and 3B) to be received in reliefs 632. External support631 further includes clearance relief surfaces 636, permitting rotationon the opposite axis. In addition, external support 631 includestrunnion 635 having an inner threaded bore 633 partly formed therein. Inaddition, flange bolt holes 637 are also formed in 631 to receive flange650 (not shown in FIG. 4, but see FIG. 2) held in place by bolts 651(FIG. 2) threaded into opening 637. To accommodate trunnions 681,openings 634 are formed in external support 631 as shown in FIG. 4B forthe insertion of trunnion 681 into openings 634 to be held in place bybearings 641 (FIG. 2).

Details of the foundation support 610 are shown in FIGS. 5A-C.Foundation support 610 accepts the outer trunnion adapter 630 andthereby restrains the SCR extension 620 to the floating or fixedstructure 300 (FIG. 1). Foundation support 610 is generally horseshoe orfoundation-friendly shaped, having back support 611 and two parallelextensions or lateral supports 612 farthest from support 612 extendingorthogonally from back support 611. The ends of lateral supports 612farthest from support 611 include recesses 613 sized to receive bearingsupport 640 therein (FIG. 2), as well as recesses 614 to receiveretainer 660 therein as shown in FIG. 5. In addition, foundation support610 includes openings 615 sized to receive in each opening aROV-friendly pin 665 locking the retainer 660 in position and foundationsupport 610 also includes a relief surface 616 to allow for movement ofSCR extension 620 and its attached parts during rotation. Detent 617 isformed in order to control the amount of material needed for thefoundation by diminishing some of the material. In assembly, outerbearing assembly 640 is received in openings 613 and is then slid overits outer surface bearings 1000, which are held in place by an outerbearing retainer 1110 which is secured by bolts 1115. The foundationsupport 610 may also be configured to adapt to existing receptacles inlieu of attaching directly by welding or other means to the structure300.

FIG. 6 depicts the various methods in which the motions of the outertrunnion adapter 630 may be accommodated. FIG. 6A is that of a higherpaired, knife-edged alternative embodiment of trunnion 635′ of trunnion635 wherein the radius and contact surfaces are composed of highstrength metallurgy to allow for high loads. Methods as described canprovide low rotational friction values. FIG. 6B illustrates the optionof a higher paired roller or low friction bearing assembly 1000. FIG. 6Cillustrates the option of a standard bushing 1000′ instead of bearing1000. Further, the bearing 1000 and bushing 1000′ incorporate the use ofconcentric and hardened segments which make the metallurgicalrequirements of the forging or casting less critical regardingmetallurgy and hardness.

FIG. 7 shows the method of assembly of the SCR extension 620 with theouter trunnion assembly 630. The illustration depicts the manner inwhich the relief was determined to allow for the inner trunnion 681 tobe passed into the outer trunnion 630 by providing relief in lieu ofexternal bolted connections. FIG. 7 shows the sequence of thatconnection, the sequence moving from left to right as one faces thepage.

FIG. 8 illustrates an alternative damper assembly 1200 attached abovethe SCR Top Connector Assembly 600 at the upper flange 670, utilizing aspacer 1210 to accommodate the thickness of the damper assembly 1200 andsupport 1201 which may be anchored to foundation 610 or directly to thestructure 300. The top view, FIG. 8A, illustrates the support system1201, which allows a high degree of angular movement. FIG. 8A alsoillustrates the top view of the damper 1200, with cover removed,identifying the outer housing 1250, the outer housing support padeyes1260, and the spacers 1210 (FIGS. 8A and 8C), which accommodate therequired diameter of the fluid swivel flange. In this case, the valve800 would connect above the damper assembly 1200.

FIG. 9 shows the top cover 1270 of outer housing 1250 removed and showsthe hydraulic damper working parts without structural components forclarity. Within the annular space 1252 (FIG. 9B) formed inside outerhousing 1250, seawater is admitted via ball check, or similar parts,1255. As the central section 1290 is moved radially off center, fluidcontained in the annular sections 1252 is restricted from motion due tospring 1292. The tolerance and configuration of the damping systemassembly provide limited flow paths, hence differential pressure of thesides of the central section to provide a damping force to externalmotions.

FIG. 10 shows the Flexible Assembly 700 being comprised of a rotaryswivel system arrangement. The configuration, as shown, allows the uppervalve 900 to remain stationary and be rigidly mounted while the lowervalve 800 moves in 3D pendular manners about the orthogonal trunnions ofthe SCR Top Connector Assembly 600, FIG. 2. As the lower valve 800 movesduring pivot motion about the outer trunnion, adapter trunnions 635 FIG.2 and FIG. 4A, rotation is allowed in swivels 750 a, 750 b, and 750 c.No rotation occurs in 750 d, 750 e, and 750 f. Swivel 750 c remains atthe same global coordinates as prior to lower valve 800 motion butallows rotation. Swivel 750 a moves as a rigid object with the lowervalve 800 motion but allows rotation. The linkage formed by the two pipesegments between the swivels causes swivel 750 b to move bothvertically, laterally, and rotate due to the fixed lengths of thelinkages made up by the pipe bends 799 and the inactive swivels 750d,750 e, and 750 f.

With motion caused by the SCR extension assembly trunnions 681, FIG. 2,FIG. 3A and FIG. 3B, swivels 750 a, 750 b, and 750 c do not rotate butact as rigid segments along with the pipe bends 799 which make up thelinkages. Swivel 750 f remains stationary vertically and laterally butallows rotation. Swivel 750 d moves as a rigid body with the upper valve800 while allowing rotation. The differential distances are accommodatedby displacement and rotation of swivel 750 e.

For combined motions, the system functions in the same manner. Theconfiguration and use are unique to this invention and application.

FIG. 11 depicts a swivel assembly which may occupy any position in theswivel arrangement described above. Any capable swivel will suffice in asatisfactory configuration. The unique feature of this swivel is the useof only one rotary seal 784. A seal backing ring 785 is provided forassembly ease. Minor bending moments caused by pressure thrust loads onthe bends 799, FIG. 10, are absorbed by the sleeve bushings 790 whichextend along the outside diameter of the internal swivel body 780. Thelongitudinal pressure thrust loads caused by the bends 799, FIG. 10, areabsorbed by the radial thrust load bushings 786, 787. The externalswivel body 760 serves as one end of the attachment to the piping systemat end 763 while the inner swivel body 780 attaches to the piping systemat 781. The addition of added seals for testing or seals to provideassurance against seawater ingress do not compromise the features orlend claim to benefits unaware to this application.

Retainer 770 is attached to the external swivel body 760 with fasteners761, 762, or other means to contain the Rotary Swivel Components.

Hardened systems at points of high contact stress to minimize sizerequirements, reduce friction, and prevent surface galling, fretting andassociated surface failures may be used. Further, SCR Top ConnectorAssembly incorporates copper alloy components or surfaces applied bycladding, and/or electrically, mechanically, or thermal applied, forapplications of seawater exposure and areas such as pivot points whichmust be free of crustacean and other sea growths. Further, SCR TopConnector utilizes a thick walled fluid conduit section with wallthickness transition to accommodate a wide variation of SCR or similarconduit wall and grade. Also, SCR Top Connector Assembly utilizes aconduit section which may incorporate either an integral or attachedtrunnion assembly to provide for variation of material properties andthickness.

SCR Top Connector Assembly utilizes a fluid containment section whichincorporates a surface of low friction materials to allow rotationalmotion preventing alignment difficulties during installation andminimizing rotational torque of the SCR during installation therebyimproving the fatigue life.

A higher paired trunnion may be used which incorporates a rocking motionwith primarily rolling motion due to the utilization of essentiallyidentical radii of the fulcrum and beam section; the components may bearranged in any manner to achieve the desired action and the materialsof the trunnion may utilize coatings or cladding such as iron carbide orceramic or non-ferrous materials to provide high wear resistance withoutsusceptibility to corrosion.

Thus, the SCR Top Connector Swivel System transforms the pendularmotions of an SCR Top Connector Load Base to three or more rotarymotions allowing the distant ends of the swivel system to be fixed orsliding for thermal expansion of the attached piping system.

Other applications associated with the object of the invention includes:electrical conduit, or an umbilical attached in the manner of an SCR.These applications would utilize the object, of this invention; however,the pressure-containing component would be substitutes for a segment toaccommodate the umbilical or conduit and limit the minimum radius whileallowing greater installation tolerances and dynamic motions.

While the best mode and preferred embodiments of the invention have beendescribed, it is to be understood that the invention is not limited,thereto, but rather is to be measured by the scope and spirit of theappended claims.

What is claimed is:
 1. A top connector assembly for attaching a catenaryriser to a sea-based platform, comprising: a foundation support securedto a portion of a sea-based platform, the foundation support providing apair of recesses thereupon; an outer trunnion adapter that is pivotablyretained upon the recesses of the foundation support to permit pivotal,pendular motion of the outer trunnion adapter with respect to thefoundation support in a first plane, the outer trunnion adapter havingan outer structural envelope that defines a central opening therein; andan inner trunnion that radially surrounds a portion of a catenary riserand is pivotably retained within the central opening of the outertrunnion adapter to permit pivotal, pendular motion of the innertrunnion and riser portion with respect to the outer trunnion adapter ina second plane.
 2. The top connector assembly of claim 1 wherein thefirst and second planes are orthogonal to each other.
 3. The topconnector assembly of claim 1 wherein the outer trunnion adapterincludes a pair of laterally-extending bearing supports that are shapedand sized to reside within said recesses in the foundation support. 4.The top connector assembly of claim 3 wherein the bearing supports eachcomprise a, knife-edge bearing member.
 5. The top connector assembly ofclaim 3 wherein the bearing supports each comprise a roller bearing. 6.The top connector assembly of claim 3 wherein the bearing supports eachcomprise a bushing.
 7. The top connector assembly of claim 3 wherein:the outer trunnion adapter further comprises a pair of reliefs that aresized to receive complimentary bearing supports therein; and the innertrunnion further comprises a pair of laterally extending bearingsupports that are received within the reliefs of the outer trunnionadapter to provide pivotal, pendular motion of the inner trunnion withrespect to the outer trunnion adapter by rotation of the inner trunnionbearing supports within the reliefs.
 8. The top connector assembly ofclaim 1 wherein the inner trunnion is rotationally mounted to a portionof a catenary riser to permit the riser portion to rotate within theinner trunnion.
 9. The top connector assembly of claim 1 wherein theinner trunnion is formed as an integral component with a riser portion.10. The top connector assembly of claim 1 further comprising a damperassembly extending from said sea-based platform for engaging a portionof a catenary riser to damp motion of the riser.
 11. The top connectorassembly of claim 1 further comprising a flexible assembly forconnecting an end of a catenary riser that is affixed to the innertrunnion to a valve, the flexible assembly comprising a plurality ofcurved pipe bends that are interconnected by swivels to accommodatemotion of the end of the catenary riser.
 12. A top connector assemblyfor attaching a catenary riser to a sea-based platform, comprising: a) afoundation support secured to a portion of a sea-based platform, thefoundation support providing a pair of lateral support portions, each ofthe lateral support portions having a recess thereupon; b) an outertrunnion adapter that is pivotably retained upon the recesses of thefoundation support to permit pivotal, pendular motion of the outertrunnion adapter with respect to the foundation support in a firstplane, the outer trunnion adapter comprising: 1) an outer structuralenvelope that defines a central opening therein, 2) a pair of reliefsformed within the central opening and being sized to receive a bearingsupport, and 3) a pair of bearing supports that project outwardly fromthe outer structural envelope; c) an inner trunnion that is pivotablyretained within the central opening of the outer trunnion adapter topermit pivotal, pendular motion of the inner trunnion and riser portionwith respect to the outer trunnion adapter in a second plane, the innertrunnion comprising: 1) a housing that radially surrounds a portion of acatenary riser, and 2) a pair of bearing supports that are sized toreside within the reliefs of the outer trunnion adapter.
 13. The topconnector assembly of claim 12 further comprising a damping assemblyextending from said sea-based platform for engaging a portion of acatenary riser to damp motion of the riser.
 14. The top connectorassembly of claim 13 wherein the damping assembly comprises a hydraulicdamping mechanism.
 15. The top connector assembly of claim 12 furthercomprising a flexible assembly for connecting an end of a catenary riserthat is affixed to the inner trunnion to a valve, the flexible assemblycomprising a plurality of curved pipe bends that are interconnected byswivels to accommodate motion of the end of the catenary riser.
 16. Thetop connector assembly of claim 12 wherein the bearing supports of saidouter trunnion adapter each comprise a knife-edge bearing member. 17.The top connector assembly of claim 12 wherein the bearing supports ofsaid outer trunnion adapter each comprise a roller bearing.
 18. The topconnector assembly of claim 12 wherein the bearing supports of saidouter trunnion adapter each comprise a bushing.
 19. A top connectorassembly for attaching a catenary riser to a sea-based platform,comprising: a foundation support secured to a portion of a sea-basedplatform; a load-bearing support joint for securing a riser to thefoundation support, the load-bearing support joint permitting pivotalpendular motion of the riser in orthogonal planes; and a flexibleassembly for connecting an end of a catenary riser to a valve, theflexible assembly comprising a plurality of curved pipe bends that areinterconnected by swivels to accommodate motion of the end of thecatenary riser.
 20. The top connector assembly of claim 19 wherein theload bearing support joint further permits rotational motion of a riser.